Technical Field
The present technology relates to a pneumatic tire that improves steering stability on snow-covered road surfaces without causing a deterioration in steering stability on dry and wet road surfaces.
Related Art
Conventionally, the object of a pneumatic tire (a tread of an automobile pneumatic tire) described in, for example, Japanese Unexamined Patent Application Publication No. H06-278412A is to reduce hydroplaning and improve winter performance. The pneumatic tire is equipped with a center block column extending in the tire circumferential direction and block columns arranged in a shoulder portion and separated from the center block column by two circumferential grooves. The pneumatic tire is devised to guide water from a center circumferential flat plane to both sides by providing grooved blocks of the center block column, the grooved blocks being made up of two groove portions that are separated from each other by an inclined groove and intersect in the center circumferential flat plane by forming an angle with the inclined groove. Moreover, this pneumatic tire is devised to discharge snow by providing circumferential grooves that extend at an acute angle with respect to the tire equatorial plane (tire circumferential flat plane).
The above-mentioned pneumatic tire disclosed in Japanese Unexamined Patent Application Publication No. H06-278412A is further equipped with grooves (groove extension portion and connecting groove) that connect with adjacent inclined grooves in the tire circumferential direction (tire rolling direction). The groove that connects with these inclined grooves becomes narrower to equalize the size of the blocks of the center block column. Although making the blocks narrower may be effective with respect to snow-covered road surfaces, there is a risk that steering stability on dry road surfaces may be reduced since the stiffness of the blocks is reduced. Additionally, there is a risk that water discharge performance is made worse and steering stability on wet road surfaces may be reduced since the grooves that connect with the inclined grooves are inclined in the direction opposite the inclined grooves and thus work against the action of the inclined grooves to guide water from the center circumferential flat plane to both sides and thus return the water to the center circumferential flat plane side.